Semi-aromatic polyamides (like those derived from phthalic acids and aliphatic diamines, i.e. polyphthalamides, or those derived from aromatic diamines and aliphatic diacids) are polymers having excellent mechanical, physical and chemical properties which make them useful for a wide variety of different applications. Besides, they generally feature the benefit of being conveniently molded into a variety of articles of varying degrees of complexity and intricacy.
In particular, semi-aromatic polyamides are good candidates for the manufacture of articles such as portable electronic devices. Portable electronic devices, such as mobile telephones, personal digital assistants, laptop computers, tablet computers, global positioning system receivers, portable games, radios, cameras, camera accessories, and the like are becoming increasingly widely used globally in many different environments. It is often important that the housings of such devices be made from materials that are able to withstand the rigors of frequent use and can meet challenging aesthetic demands while not interfering with their intended operability. It is often desirable that those materials have good stiffness and high impact resistance, and that they exhibit high dimensional stability when they are formed (as by injection molding, for example) into housings.
Many attempts have been made to offer a polyamide material suitable for the manufacture of portable electronic devices housings. Most of them offer a very good balance of properties useful in these specific applications.
However, these prior art housings still suffer from a significant drawback: they are not resistant to staining agents that are often put in contact with these portable electronic devices housings. Typical staining agents include: makeup (such as lipstick, lip gloss, lip liner, lip plumper, lip balm, foundation, powder, blush), artificial or natural colorants (such as those found in soft drinks, coffee, red wine, mustard, ketchup and tomato sauce), dyes and pigments (such as those found in dyed textiles and leather, used for the manufacture of portable electronic devices housings). In contact with these staining agents, the prior art articles, and in particular the portable electronic devices housings are easily stained.
The staining issue of polyamides is known for a long time but in a different application, namely in the field of carpet and textile fibers. Polyamide fibers are relatively inexpensive and offer a desirable combination of qualities such as durability, comfort, and ease of manufacture into a broad range of colors, patterns, and textures. As a result, polyamide fibers are widely used in the home and industry as carpets, drapery material, upholstery, and clothing. Carpets made from polyamide fibers are a popular floor covering for residential and commercial applications.
Polyamide fibers dye easily with dyes. Consequently, carpets made from polyamide fibers stain easily when exposed to dyes or staining agents that exist in some common food and beverages. The resulting stains cannot be easily removed under ordinary cleaning conditions. The severe staining of carpeting is a major problem for consumers. In fact, surveys show that more carpets are replaced because of staining than because of wear.
Many attempts have been made to offer anti-staining polyamide carpets and textiles that resist common household and common stains, thereby increasing their life. For example, one way of avoiding such staining is to topically apply to the surface of the polyamide filaments materials a specific anti-staining agent. U.S. Pat. No. 6,488,893 provides for example a solution comprising condensation product of sulfonated naphthalene sulphonic acid, and aldehyde and a dihydroxydiphenyl sulfone together with a methacrylic acid polymer that function as stain blockers so as to prevent stains from permanently coloring the yarn. Topical treatments, however, tend to be costly and non-permanent (washed away with one or more washings).
It would thus be desirable to obtain articles and in particular housings for portable electronic devices that are made from polyamide compositions having excellent stiffness, high dimensional stability and impact resistance while exhibiting also anti-staining properties.
It is thus a first object of the present invention to provide anti-staining polyamide articles. The polymer composition (C) according to the present invention exhibits outstanding properties: good mechanical properties, high temperature resistance, low water absorption, superior chemical resistance. It can also be easily processed and may be molded into thin walls. In addition, the inventors have surprisingly found that the polymer composition (C) according to the present invention features also outstanding anti-staining properties.